The present invention relates to a compressor that accommodates a piston within each of a plurality of cylinder bores laid out around a rotary shaft, and that has shoes disposed between a swash plate that rotates integrally with the rotary shaft and each piston. The shoes are in a sliding contact with both the swash plate and the piston, thereby to reciprocally move the piston by transmitting the rotation force of the swash plate to the piston via the shoes.
In a compressor for reciprocally moving the piston based on a rotation of a swash plate that integrally rotates with the rotary shaft and that can change its inclination angle, it is possible to change a discharge capacity of this compressor. An example of a device for driving the rotary shaft of such a variable displacement type compressor by a motor has been disclosed in Japanese Unexamined Patent Publication No. 5-187356.
The device disclosed in Japanese Unexamined Patent Publication No. 5-187356 corresponds to what is called a wobble type. According to this device, a piston support makes an inclined movement based on the rotation of the swash plate so that the piston makes a reciprocating motion by this inclined movement. A compressive reaction force generated at the time of discharging a gas from each cylinder bore works on the reciprocating motion mechanism for reciprocally moving the piston. A mechanism of reciprocally moving the piston by transmitting the inclination movement of the rotating swash plate to the piston via the non-rotating piston support is complex. A guide groove is formed on a drive plate that is fixed to the rotary shaft, and a pivot pin fixed to the swash plate is engaged with the guide groove. A sleeve is slid ably supported by the rotary shaft. The sleeve supports the swash plate so that the swash plate can make an inclination movement via a sleeve pin that is formed on the sleeve. The inclination movement of the swash plate is guided by the engagement between the guide groove and the pivot pin and the sliding of the sleeve. The drive plate receives the compressive reaction force via the piston, the piston support, a thrust bearing, the swash plate and the pivot pin respectively.
In the case of driving the rotary shaft of the wobble-type variable-displacement type compressor by using a motor, it is essential to minimize the rotational friction between the swash plate and the piston support as far as possible. Otherwise, it is necessary to use a large motor having a large output, which results in a large compressor as a whole. Particularly, when carbon dioxide is used as a refrigerant, an extremely large compression is necessary at a high pressure. This generates a large frictional force. Therefore, it is essential to dispose a thrust bearing between the swash plate and the piston support. This structure increases the length of the compressor.
It is an object of the present invention to provide a compact motor-operated compressor.
In order to achieve this object, according to the present invention, there is provided a motor-operated compressor that accommodates a piston within each of a plurality of cylinder bores laid out around a rotary shaft, and that has a shoe disposed between a swash plate that rotates integrally with the rotary shaft and each piston so that the shoe is in a sliding contact with both the swash plate and the piston, thereby to reciprocally move the piston by transmitting the rotational force of the swash plate to the piston via the shoe, wherein the piston for making a reciprocating motion is a single-headed piston that discharges a gas from the cylinder bores only during a forward motion, and the rotary shaft is driven by a motor.
The structure of transmitting the rotational force of the swash plate to the single-headed piston via the shoe is advantageous for making compact the compressor that is driven by the motor.
The present invention will be more fully understood from the following description of preferred embodiments as well as the attached drawings of the present invention.